A new synergy algorithm has been recently developed, to retrieve Aerosol Optical Thickness (AOT) in high spatial resolution (1 km × 1 km), which may improve the study of aerosols at local scale. The algorithm combines spectral and angular information provided by the MERIS and the AATSR sensors, respectively, offering improved characterization of aerosol properties. In the present study, the MERIS/AATSR synergy algorithm was validated by comparing the retrieved AOT with the respective AOT values observed at AERONET stations globally, considering different land cover types. Spatial patterns and differences between the MERIS/AATSR and the MODIS derived AOT were also investigated. Results indicated that the MERIS/AATSR synergy algorithm substantially improves the spatial resolution of the derived AOT and it is capable of retrieving AOT for most land cover types, with a good correlation relative to AERONET station measurements (R² ranges between 0.60 and 0.90, depending on the land cover type).